This invention relates to a rain or moisture sensor for a vehicle windshield incorporated in a wiper control system for modifying wiper operation on the basis of detected moisture on the windshield. In particular, it relates to such an apparatus whereby a sensor of the resistive type on the outside surface of the windshield is coupled capacitively through at least one layer of glass in the windshield to wiper control apparatus within the vehicle.
Resistive rain sensors for wiper systems are known in which a pair of conducting members on the outside of the windshield within the wiped area are separated slightly so as to be insulated from each other when dry with the separation being bridged by conducting water droplets when wet to greatly decrease the resistance therebetween. An electrical circuit includes the conducting members so as to be responsive to the series resistance thereof and modify wiper action by initiating wiper operation or decreasing wiper pause time in intermittent operation when the series resistance is decreased by the presence of water on the outside of the windshield bridging the conducting members. The conducting members on the outside of the windshield, however, must be electrically connected in some way to the wiper control within the vehicle, which connection may be by means of connectors routed in an unsightly manner across the outer surface of the windshield from the sensor or may require an opening formed through the windshield.